1. Field of the Invention
The present invention relates to a shutter for use in a camera.
2. Description of the Related Art
Conventional shutters which have been widely used in compact cameras are designed to use a single shutter speed and enable the aperture of the exposure opening to change between two levels in accordance with the change of ISO sensitivity, ambient brightness, etc. To obtain two different levels of aperture, the conventional practice is to provide two different levels for the amount of rotation of a pulse motor, or to prepare two driving motors for two different aperture levels. A shutter mechanism has recently been proposed which has a plurality of shutter blades provided with first and second opening forming portions so that when a motor is rotated in a first direction, a lens opening is formed by the first opening forming portions, whereas, when the motor is rotated in a second direction, a lens opening having a different aperture is formed by the second opening forming portions [see Japanese Patent Laid-Open (KOKAI) No.04-116533 (1992)].
In a case where the pulse motor is controlled so as to provide two different amounts of rotation as in the conventional shutters, however, when the motor is stopped with the shutter opening set to the first aperture level, hunting occurs, which makes it difficult to effect exposure control. When two pulse motors are used, the number of parts increases, resulting in an increase of the cost.
In contrast, the shutter mechanism, in which two different opening forming portions are provided and a motor is selectively rotated in forward and backward directions, is free from the problems of hunting and cost. On the other hand, since the shutter blades are adapted to reciprocate in two directions with respect to the lens opening, the space required for the movement of the shutter blades increases, which is an obstacle to reduction in the overall size of the camera.